You are being pulled by the low pressure area created by the bus.
Much the same whay an airplane wing works.
Low pressure on one side and high pressure on the other creates lift.

Enjoy

On the discussion board of the movie at IMDB there is some hilarious stuff, including a guy's 'personal racing history' (same guy who, if I recall, has some commentary regarding yokels' reactions to a cross-dressing or trans-gender cyclist). Also directions on how to get to the quarry if you're ever in Bloomington.

You need to get some age on you, boy. Look at when the movie was made. If he was lucky and rich, the rear cog may have been a 13 and the front one whould have been a 40. More likely the rear cog was a 14. Young pups! (Shaking his cane from the porch.) :D

I exceeded 40 mph drafting an RV on a level arterial road. It had turned off the same side road I was on, and because it accelerated gradually and there were no road junctions on the stretch ahead, i.e. I was pretty confident it would maintain speed, I kept up with it until we reached an incline.

I don't think I would do it again, since a bike doesn't brake as well as most motor vehicles. But it was fun just to have tried it once.

Drag is a force, yes, but we don't really have to worry about force when we ride.
That's what gearing is for.
Instead, we're mainly concerned with power. And power is force times speed.
So, we have speed multiplied into the whole thing a third time, making the power dependent on speed cubed.
If the power required to go 5 mph is 125 (made-up, unit-less number), then you need a power of 1000 to go 10 mph. And 8000 to go 20 mph. This is the aerodynamic drag/power only.
Rolling power increases linearly with speed, so going twice as fast just means twice the power. That power is added to the aerodynamic power.

When and object moves through a fluid (air, water, et c) it affects the fluid around it.
The air within the boundary layer "sticks" to the surface of the object and is continually set in motion in the direction of the moving object. After the moving air slips off of the object, it is still in motion forward. This forward motion slowly returns to normal local air speed some distance behind the first object. Any object following behind, within this distance, will experience a lower relative air speed, and that translates to a lower drag force and less power required.
This drag is known as friction drag. Unless you have two (for the purpose) highly optimised objects, very close together, this type of drag is not lessened by the object behind.

A bluff object also has plenty of form drag, which is the difference in pressure between the front of the object and the rear of the object. The pressure by the oncoming relative wind on the front of the moving object is a force, and it acts to slow the object. If there's an equal amount of pressure from the air on the rear half of the object, the two forces cancel out, and there is no drag.
This is known as pressure recovery, and the main purpose of aerodynamic shapes is to maximise it.
Pressure drag, like friction drag, can't be eliminated.
If another object is close behind the first, its moving through the air creates a kind of "bow wave" where the air slows down (stagnation) relative to the free air far away. This slower air helps the object in front with its pressure recovery, since the lower relative wind means the negative pressure is lower.

Thus, both objects gain from being close, though not equally much.

The larger and boxier the object in front, the more you gain!

Did I mention I have 180 mm cranks? For me (37" inseam) I think it would be impossible. However, since my new computer can display cadence, I will certainly try. Thanks for the inspiration!

The last time I checked, when the wind pushes against you, it's a force. I'm glad you don't have to worry about this opposing force but the rest of us who live in reality will unfortunately have to deal with the opposing force of air pushing against us every time we ride.
There is a difference between the force you put down on your pedals and the force of the air pushing against you. You've confused the two. One you would use gearing to overcome, the other.. other than getting more aerodynamic, I'm not sure if there are any other ways to overcome wind resistance.

Ride your bike on the moon?

Apparently I'm wrong... I stand corrected.

You could also cycle underwater.

Well they could've been brek'n the wind...I wasn't there :p

Yes, it's a force, but you don't run out of force in your legs, you run out of power (provided you have sufficient gearing), so force isn't as interesting as power here.
Of course, the drag force is "two thirds" of the power, so it's important for sure, but it's not really what we fight against when we pedal. Our effort pedalling is the power required, but the force we're pushing down the pedals with depends mostly on gearing, and is limited at the lower end by the cadence we're comfortable with.